In recent years, digital contents including music and images are dealt with in various types of devices. Such devices are able to duplicate and edit digital contents without degrading the contents. It is necessary, however, that these digital contents are dealt with while being protected, from the viewpoint of copyrights.
A conventional technique is disclosed in which a data processing apparatus switches between a secure mode and a normal mode by a monitor, the secure mode being a mode in which secure data that needs to be protected and a secure application that needs to be protected are accessible, and the normal mode being a mode in which the secure data and the secure application are not accessible. According to this technique, the application that operates in the normal mode requests the secure application to process data via an operating system that operates in the normal mode. The operation system requests the monitor to switch the execution modes, and the monitor switches the execution modes. The secure application performs the requested processing and returns the processing results to the application via a secure operating system that operates in the secure mode. The secure operating system requests the monitor to switch the execution modes, and the monitor switches the execution modes. With this configuration, since execution is switched between the secure mode and the normal mode, it is not possible to access the secure data and the secure application directly from the application that operates in the normal mode. Accordingly, it is possible to protect the secure data and the secure application.    Non-Patent Document 1: A New Foundation for CPU Systems Security (searched on Nov. 20, 2003—URL: http://www.arm.com/armtech.nsf/htmlall/FC4C07580E29428080256D1A004A2345/$File/TrustZone_WP.pdf?OpenElement)